Fluid pressure cylinders having load responsive piston valves



July 2. 1968 Filed Oct. 19, 1965 W. l... HAMMER FLUID PRESSURE CYLINDERSHAVING LOAD 2 Sheets-Sheet 1 /6 it 9a /V// L 20 J g /9 4 Y Z, COMPRE 13; .3 3

5o /7 3o /6 52 v 53 Farm Posrow INVENTOR WILLIAM L. HAMMER July 2. 1968w. L. HAMMER 3,390,616

FLUID PRESSURE CYLINDERS HAVING LOAD RESPONSIVE PISTON VALVES Filed Oct.19, 1965 2 Sheets-Sheet 2 jay.

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aag r So-H-W'G l l I I ll 49 1 1: l I u---- 45 :tiiT" INVENTOR coMPWILLIAM L. HAMMER ATTORNEY S United States Patent 3,390,616 FLUIDPRESSURE CYLINDERS HAVING LOAD RESPONSIVE PISTON VALVES William L.Hammer, 6513 Betsy Ross Place, Wauwatosa, Wis. 53213 Filed Get. 19,1965, Ser. No. 498,023 11 Claims. (Cl. 91- 122) ABSTRACT OF THEDISCLOSURE A double-acting fluid pressure cylinder having a pistonoperatively connected to a load, there being a chamber on each side ofthe piston and the piston having a fluid chamber therein with ductsnormally closed by check valves leading from each cylinder chamber tothe piston chamber, the inner end or" the piston rod being slida-ble inthe piston and having a valve-controlled passageway affordingcommunication between one of the cylinder chambers and the pistonchamber when the piston rod is in one position of slidable movement, andanother valvecontrolled passageway affording communication between theother cylinder chamber and the piston chamber when the piston rod is inanother position of movement.

This invention relates to improvements in fluid pressure cylindershaving load responsive piston valves.

A pneumatic system has many advantages, such as load cushioning.However, such load cushioning becomes a disadvantage when a pneumaticcylinder is operating in connection with an overrunning load. When theload overruns the pneumatic cylinder, as happens after the load passesdead center, the load is acted on by gravity, causing the piston tocompress air. Thereafter the cylinder loses control of the load until abalance is obtained. Because of the above problem it has usually beennecessary to use hydraulic systems in this type of situation.

It is a general object of the present invention to provide an improvedpneumatic cylinder having improved means for preventing uncontrolledload surges when the cylinder is being used with an overrunning load.

A more specific object of the invention is to provide an improved fluidpressure cylinder wherein the piston has a novel valve automaticallyoperable so that it is possible to introduce fluid under pressure intoboth sides of the cylinder whereby there is flow of fluid under pressurethrough the piston which flow can be controlled as a function of whetherthe piston rod is in tension or compression during control of theoverrunning load.

A further specific object of the invention is to provide an improvedpneumatic cylinder as above described wherein the valve means in thepiston includes check valves which enable the cylinder to operate inboth directions.

A further object of the invention is to provide an improved pneumaticcylinder as above described wherein a portion of the valve mechanism isembodied in the inner end of the piston rod.

With the above and other objects in view the invention consists of theimproved fluid pressure cylinder having a load responsive piston valve,and all of its parts and combinations, as set forth in the claims, andall equivalents thereof.

In the accompanying drawings, illustrating several em- 3,399,616Patented July 2, 1968 See bodiments of the invention, in which the samereference numerals designate the same parts in all of the views:

FIG. 1 is a longitudinal sectional view through an improved pneumaticcylinder showing the piston at the start of a load controlling movement,with the piston rod under compression as it is being pushed by thepiston;

FIG. 2 is a sectional view of the piston taken approximately on the line22 of FIG. 1;

FIG. 3 is a sectional view taken approximate-1y on the line 33 of FIG.1;

FIG. 4 is a partially diagrammatic longitudinal sectional view throughthe cylinder, showing an advanced position from FIG. 1, in which thepiston has been moved to the right and in which the load has juststarted to overrun the rod to exert a pull thereon so that the rod isnow under tension;

FIG. 5 is a view similar to FIG. 4 wherein the piston is still fartheradvanced as the load continues its pull on the piston rod, the latterbeing under tension;

FIG. 6 is a view similar to FIG. 5 at the start of a reverse movementafter compressed air has been admitted into the right hand chamber sothat thepull on the rod is now from the piston, with the rod undertension;

FIG. 7 is a similar view of the return movement showing the piston in anadvanced position from FIG. 6, the load having overrun the rod so thatthe load now exerts a push on the rod and piston with the rod undercompression;

FIG. 8 is a similar view showing further return movement, with the pushstill exerted by the ove-rrunning load and the rod in compression;

FIG. 9 is a partially schematic end View of .a utility truck showing theinvention applied to a ladder loading mechanism, the dotted linesindicating the position of the parts when the ladder mechanism islowered; and

FIG. 10 is a partially schematic view showing the cab end of a tiltingcab truck, and illustrating the application of the invention to thecontrol of a tiltable cab, the dotted lines indicating the position ofthe parts when the cab is tilted.

Referring more particularly to the drawings, the numeral designates asuitable pneumatic cylinder having oppositely disposed ports 16 and 17.Suitably guided for sliding movement through the end 18 of the cylinderis a piston rod 19 having its inner end operatively associated with thenovel piston 20.

Thepiston has a central bore 21 for slidably receiving the inner end ofthe piston rod 19. The bore communicates with an interior chamber 22.The chamber 22 communicates through radial passageways 23 with axiallydirected bores 24 which are in communication with the right hand chamber25 of the cylinder. At the inner end of each bore 24 is a valve seat 26controlled by a valve member, such as the ball 27, which is normallyurged into closing position by a light spring 28.

The interior chamber 22 is also connected by spaced radial ducts 29which alternate with the ducts 23, as shown in FIG. 2, with axial bores30 communicating with the left hand cylinder chamber 31. At the innerend of each bore 39 is a valve seat 32 controlled by a valve such as theball 33 which is normally urged to closing osition by A a light spring33.

The inner end of the piston rod is in the form of a spool, speciallyconstructed to coact with the improved piston in forming a spool valve.Such inner end of the rod has separated but aligned axial passageways 34and 35. One end of the passageway 34 communicates with radialpassageways 36, and the other end communicates with like radialpassageways 37. The inner end of the bore 35 connects with radialpassageways 38. On the inner end of the piston rod is a rigid thrustcollar 39 which is slidable Within a cup 40 projecting from the lefthand face of the piston. Another thrust collar 41 on the piston rod isslidable in a cup-shaped portion 42 projecting from the right hand faceof the piston. The arrangement of the collars 39 and 41 and ports 36, 37and 38 is such that when the ports 37 are in communication with theinterior piston chamber 22 the ports 38 are closed by the adjacentpiston wall portions, the ports 36 always being open to the chamber 25.When, however, the piston rod is moved to the right, as in FIG. 4, thenthe ports 37 are closed and the ports 33 are in communication with theinterior piston chamber 22. In the position of FIG. 1 the thrust collar41 is against the right face of the piston to receive thrust therefrom.When the parts are in the position of FIG. 4 the thrust collar 39 is incontact with the left hand face of the piston. Each of the collars 41and 39 is provided with air relief ports 43.

OPERATION In operation, assuming that the valve 51 is set to admitcompressed air into the port 16 from a suitable source 52 of compressedair to the left hand chamber 31 of the cylinder, this will cause anincrease of air pressure in the chamber 31 from zero to something lessthan 90 p.s.i., for example, which pressure acts on the left hand faceof the piston to cause the piston and piston rod to move toward theright, referring to FIG. 1. For purposes of illustration, the cylinder15 has been shown in FIG. 9 as pivotally connected at one end, as at 44,to an upper portion of a utility truck 45. The piston rod 19 ispivotally connected as at 46 to a pivot bracket 47, there being asimilar bracket spaced forwardly on the truck from the bracket 47, whichbrackets are pivoted to the truck as at 47. Pivotally connected as at4-8 to the brackets 47 is the upper longitudinal edge of a cradle 49 fora ladder set 50.

As the piston rod 19 moves to the right from the position of FIG. 1, itwill act to cause pivoting of the brackets 47 in a clockwise directionabout the pivots 47. During such movement the piston rod 19 is undercompression. The check valves 33 are closed because of the ressure inthe chamber 31 and the check valves 27 on the other side are alsomaintained closed. The passageways 38 are closed in the position of FIG.1 so that the 90 p.s.i. air in the chamber 31 cannot enter the interiorchamber 22 of the piston. During such movement the valve 53 ismanipulated to cause exhausting through the exhaust line 54 and to shutoff communication between the source of compressed air 52 and the port17. If desired the valve 53 may be in an only partially open position toretard the movement, depending upon requirements.

As soon as the brackets 47 and ladder cradle 49 are over dead centerwith respect to the pivots 47' gravity will act so that the overrunningload pulls the piston rod 19 in tension, causing the collar 39 on theleft hand end of the piston rod to be pulled into contact with the lefthand face of the piston 2% so that the load now exerts a pull on thepiston. During such shift of the piston rod with respect to the pistonthe radial ports 37 are now blocked off while the ports 38 are movedinto communication with the interior piston chamber 22. 90 p.s.i. airfrom the left chamber 31 can now pass through the axial bore 35 at theleft end of the piston rod, as shown in FIG. 4, through the radial ports38, into the piston chamber 22, forcing the ball valves 27 to openposition to allow 90 p.s.i. air to enter into the right chamber 25.\Vith the valve 53 now turned to a position to close the exhaust port17, the pressure in said chamber eventually builds up. Force on thepiston from differential pressure is now at a minimum and theoverrunning load causes the pressure in the right chamber to exceedp.s.i. When this occurs the force in the right hand chamber 25 is suchas to close the right hand ball valves 27, as shown in FIG. 5, causingthe piston to now brake the load. This action speeds up the compressionin the right chamber 25 to more quickly cushion the force of theoverrunning load. Thus there is automatic control of the overrunningload inherent in the valve of the piston. During such cushioning action,illustrated in FIG. 5, it is desirable to close the inlet valve 51 aswell as the exhaust valve 53. Thereafter it is customary to open thevalves 51 and 53 to relieve pressure within the chambers 31 and 25.

After the load has been stopped in the dotted line position of FIG. 9the ladders are now in a lowered position convenient for use. After theladders have been used and replaced in the cradle 49 the improvedmechanism permits ready return movement. This is accomplished by turningthe valve 53 to a position to admit compressed air from the source 52 tothe right hand chamber 2 5, as in FIG. 6, at 90 p.s.i., for example,causing the pressure in the chamber 25 to increase from zero tosomething less than 90 p.s.i. This increase in air pressure on the rightface of the piston 20 causes the piston to move toward the left, withthe piston pulling the load to cause a raising of the ladder cradles inFIG. 9. During such movement the piston rod is in tension and the checkvalves 27 and 33 are maintained in seated position. Also the radialports 37 are blocked off while the radial ports 38 are in communicationwith the central chamber. With the three-way valve 51, which controlsflow from the port 16 on the left side, in open or partially openposition, air will be exhausted through the exhaust line 55.

The air pressure in chamber 25 moves the piston to the left, asindicated in FIG. 7, and as soon as the ladder cradle swings to such apoint that the load is over dead center with respect to the pivot 47 ofFIG. 9, the load is in overrunning condition and pushes the piston rodin compression, as shown in FIG. 7, shifting the spool valve within thepiston to the position shown in FIG. 7. In such position the 90 p.s.i.air in the right chamber 25 can now travel by way of the ports 36,through the axial bore 34 of the piston rod and out of the radial ports37 into the central chamber 22 of the piston. From this chamber the 90p.s.i. air will pass out past the opened ball valves 33 into the leftchamber 31, causing the pressure to build up in the left chamber and.reducing the force on the piston from differential pressure which is nowat a minimum. The piston then moves toward the position of FIG. 8, andwith the valve 51 now closed or partly closed air pressure in the leftsection increases to a point in excess of 90 p.s.i. When this occurs allof the check valves in the piston close, as in FIG. 8, and the pistonnow serves to brake the load. By thereafter closing both of the valves51 and 53 the load will cushion against the air in the chamber 31, whichcushioning action was speeded up by bypassing the high pressure air fromthe right hand chamher to the left hand chamber. The load will now bereturned to the full line position of FIG. 9.

The valves 51 and 53 may be opened and closed either manually or throughsuitable automatic mechanism depending upon the application to which thedevice is put.

Referring to FIG. 10, the invention is well adapted to use incontrolling the tilting of a tiltable cab on a motor truck. Such truckscommonly have a source of compressed air 52' for supplying compressedair to the air brakes. This same source can be conveniently used inconjunction with one of the pneumatic cylinders 15 of the presentinvention, which may be pivoted to the frame as at 56 and have itspiston rod pivoted to the tilting cab as at 57, the latter beingtiltable on the pivot 58.

While only two uses for the invention have been illustrated, it isobvious that the improved fluid pressure cylinder may have use in manyother applications where problems of overrunning loads are encounteredand is also useful in connection with hydraulic cylinders. It is alsoapparent that when used with a pneumatic cylinder the sponginess of apneumatic system is effectively reduced by the bypassing of highpressure air into the exhaust end of the cylinder at the time when theoverrunning load takes over to better control such overrunning movement.It is also apparent that the improved piston valve in effect is able todistinguish between a compression and tension load on the piston rod toautomatically cause the valve to shift as soon as the overrunning loadtravels over center, thus quickly cushioning the over center force fromthe load.

Various changes and modifications may be made without departing from thespirit of the invention and all of such changes are contemplated as maycome within the scope of the claims.

What I claim is:

1. In combination with a movable load, means including a fluid pressurecylinder operatively connected to said load for controlling the movementof the same, said cylinder having a piston therein with a piston rod andhaving a chamber on each side of said piston, means for introducingfluid under pressure into a first one of said chambers to urge saidpiston and rod in one direction, said piston having a fluid chambertherein with check valve ducts leading to said piston chamber from eachcylinder chamber, check valve means normally preventing flow throughcheck valve ducts from one cylinder chamber into said piston chamber,check valve means normally preventing flow through check valve ductsfrom said other cylinder chamber into said piston chamber, an additionalfluid conduit between each cylinder chamber and said piston chamber, andmeans including valves in said piston controlling flow through said lastconduits and responsive to a change from compression to tension on thepiston rod as a result of movement of the load to admit said fluid underpressure from one chamber of the cylinder via said piston chamber to theopposite cylinder chamber through the check valve ducts thereof to aidin controlling movement of the load.

2. A device as claimed in claim 1 in which there is exhaust meansassociated with the other cylinder chamber, and a valve for controllingsaid exhaust means.

3. A device as claimed in claim 1 in which the cylinder is a pneumaticcylinder and in which the fluid under pressure is compressed air.

4. In combination with a load mounted for movement from a positio on oneside of dead center to an overrunning position on the other side, meansincluding a fluid pressure cylinder operatively connected to said loadfor controlling the movement of the same, said cylinder having a pistontherein with a piston rod and having a chamber on each side of saidpiston, means for introducing fiuid under pressure into a first one ofsaid chambers to urge said piston and rod in one direction, said pistonhaving a fluid chamber therein with check valve ducts leading to saidpiston chamber from each cylinder chamber, check valve means normallypreventing flow through said check valve ducts from one cylinder chamberinto said piston chamber, check valve means normally preventing flowthrough check valve ducts from said other cylinder chamber into saidpiston chamber, an additional fluid conduit between each cylinderchamber and said piston chamber, and means including valves in saidpiston controlling flow through said last conduits and responsive toforces resulting from movement of the load from one side of dead centerto the other to admit said fluid under pressure from said first chamberof the cylinder via said piston chamber to the opposite cylinder chamberthrough the check valve ducts thereof to aid in control of theoverrunning load.

5. A device as claimed in claim 3 in which the load is a pivoted ladderloading mechanism.

6. A device as claimed in claim 3 in which the load is a tiltablymounted truck cab.

7., A device as claimed in claim 4 in which the cylinder is a pneumaticcylinder and in which the fluid under pressure is compressed air.

8. In combination with a load mounted for movement from a position onone side of dead center to an overrunning position on the opposite side,means including a fluid pressure cylinder operatively connected to saidload for controlling the movement of the same, said cylinder having apiston therein with a piston rod and having a chamber on each side ofsaid piston, means for introducing fluid under pressure into a first oneof said chambers to urge said piston and rod in one direction, saidpiston having a fluid chamber therein with check valve ducts leading tosaid piston chamber from each cylinder cham ber, check valve meansnormally preventing flow through check valve ducts from one cylinderchamber into said piston chamber, check valve means normally preventingflow through check valve ducts from said other cylinder chamber intosaid piston chamber, an additional fluid conduit between each cylinderchamber and said piston chamber, a piston rod having its inner endaxially slidable in said piston, spaced thrust collars on said rodpositioned for alternative engagement with one side of the piston or theother as a result of relative sliding movement between the piston rodand piston, and cooperating valve means in said piston and inner end ofthe piston rod operative as a result of said relative sliding movementto admit said fluid under pressure from one chamber of the cylinder viasaid piston chamber to the opposite cylinder chamber through check valveducts in response to forces on the piston rod resulting from movement ofthe load from one side of dead center to the other to thereby aid incontrolling the overrunning load.

9. The device as claimed in claim 6 in which the valve means is in theform of a spool valve.

10. The device as claimed in claim 8 in which the cylinder is apneumatic cylinder and in which the fluid under pressure is compressedair.

11. In combination with a load mounted for movement from a position onone side of dead center to an overrunning position on the other side,means including a double-acting pneumatic cylinder operatively connectedto said load for controlling the movement of the same, said cylinderhaving a piston therein with a piston rod and having a chamber on eachside of said piston with a gas port in communication with each chamber,said piston having a valve chamber therein, a source of compressed gas,a pneumatic circuit between said source and ports, valve means forcontrolling the flow of gas from said source into each port, each valvemeans having a shut-01f position and an exhaust position, and meansincluding a valve in said piston controlling flow through the valvechamber in the piston and responsive to forces on said piston rodresulting from movement of the load from one side of dead center to theother to admit compressed gas from one of said chambers of the cylinderto the other chamber, depending upon the direction of operation of thedouble-acting cylinder, to aid in control of the overrunning load, theinner end of the piston rod being slidable in the piston and the pistonincluding the following:

at least one duct between said piston valve chamber and one of thecylinder chambers;

non-return check valve means controlling said ducts and normally closedas a result of pressure in the adjacent cylinder chamber;

at least one duct between said valve chamber of the piston and the othercylinder chamber;

non-return check valve means controlling said last ducts and normallyclosed under pressure in the adjacent cylinder chamber;

passageways in the inner end of the piston rod independent of said checkvalve ducts affording communication between one of the said cylinderchambers and the piston chamber when the rod is in one position ofslidable movement with respect to the piston; and

passageways in the inner end of the piston rod independent of said checkvalve ducts affording communication between the other cylinder chamberand the piston chamber of the piston when the piston rod is in anotherposition of slidable movement with respect to the piston.

References (Iited UNETED STATES PATENTS 2,646,025 7/1953 Deardorif91-436 Banker 91422 Hoffmann 91422 Tennis 91436 Augustin 91-422 Acker eta1 91422 MARTIN P. SCHWADRON, Primary Examiner.

EDGAR W. GEOGHEGAN, Examiner. B. L. ADAMS, Assistant Examiner.

